WILLIAM GREIDER has done a service for Americans who want a better understanding of why they have negative feelings about the political system.

He has taken a hard look at the various lead players in that system - Congress, political parties, executive-branch regulators, and especially corporation lobbyists - and come up with a critique that ought to arouse anyone's patriotic indignation.

Greider's perspective - "the betrayal of American democracy," as his subtitle puts it - is shaped by 30 years of accumulated skepticism as a newspaper reporter and editor. He's a former assistant managing editor of the Washington Post and a regular contributor to Rolling Stone. His politics, one suspects, are unfailingly liberal - but "Who Will Tell the People" can't be pushed aside as a predictable lament from the left.

Greider has probed his subject thoroughly. He raises questions that every American who retains a faith in the self-correcting capacities of democracy (and Greider is firmly among them) ought to confront.

Take, for instance, his central theme that powerful "elites" - those capable of making huge financial contributions to today's money-run politics - are shaping the public agenda and even the laws themselves.

" `Client' has a different meaning from `constituent' or `citizen,' but the word accurately describes the common relationships that define contemporary politics," writes Greider. His prize exhibit, of course, is the savings and loan scandal, which provides examples of even the most upright members of Congress being misled by "client" bankers back home.

But the problem goes far beyond the old story of lawmakers being corralled by special interests, according to Greider. It's that these interests, particularly the biggest, wealthiest business interests in the country, have become masters of their own brand of "grass roots" politics. They can turn out polls, letter-writing campaigns, man-on-the-street testimonials, and participants at regulatory hearings better than most public-interest lobbies ever dreamed of doing. And they can tap huge reservoirs of ex pertise and "factual" information collected at research institutes dependent on their funding.

Greider calls this "information-driven politics," which "cannot produce a satisfying democracy because it inevitably fosters its own hierarchy of influence, based on class and money."

The fundamental problem, he says, is that the little guy simply can't be heard in this environment.

The views of average citizens whose common sense tells them that toxic dumping has gotten out of hand or that free trade threatens loss of jobs are dismissed as "emotional." People feel distanced from the government that supposedly draws its legitimacy from "We the People."

Greider firmly believes that even reforms that come under the banner of popular backing, such as the federal tax cuts of the early 1980s, end up serving the monied interests, not the average person. He traces the last 10 years of tax policy and finds a persistent bias toward the wealthy - for example, the big, regressive increases in Social Security payroll taxes versus the inability to push through income-tax hikes for the wealthiest few.

As anyone who follows economic analyses knows, the figures on tax burdens and income trends shift according to who's crunching them.

But Greider's assessment is a compelling one. It demands a hearing, especially at a time when virtually all candidates for president are lining up behind some form of capital-gains tax relief and various investment incentives.

The bulk of "Who Will Tell the People" is filled with hard-eyed looks at institutions - from the Democratic Party (just as deeply indebted to corporate interests as the Republicans) to the General Electric company (a case study of effective corporate activism) to his colleagues in the press (who are, in his view, much too cozy with the people in power). But Greider also has a few prescriptions for change, prominent among them the type of local political organization typified by the Industrial Areas Found ation, the movement started in Chicago by Saul Alinsky.

The book ends with a rousing call for Americans, most of whom are what Greider calls "passive consumers of politics," to renew the "democratic dialogue" - not just for their own sake, but for the millions elsewhere who are struggling toward democracy.

"Power can accumulate in mysterious ways," the author says, "if citizens believe they possess this right. Their power atrophies when they no longer believe in it. This book is for the believers."